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CVE-2026-64567NVD status: Analyzed

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-64567 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 8ded74c654a982dc8581a17b0caa7fcedb20de69, c9c38066b6446e83668c041702bb639b0ca49363, 094734c7aaa2b36751dc32480a680a4952685e78 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 8ded74c654a982dc8581a17b0caa7fcedb20de69 or c9c38066b6446e83668c041702bb639b0ca49363 or 094734c7aaa2b36751dc32480a680a4952685e78 or 33878ba25e2638bc0c61623d7a05c9ca2b74c039, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.265 or 5.15.216 or 6.1.183 or 6.6.148, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, 8ded74c654a982dc8581a17b0caa7fcedb20de69; 5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, c9c38066b6446e83668c041702bb639b0ca49363; 5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, 094734c7aaa2b36751dc32480a680a4952685e78; 5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, 33878ba25e2638bc0c61623d7a05c9ca2b74c039; 5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, 404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2; 5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, 5e1b2ca6b34939e70fb0785e8222b53cf060016f; 5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, f9fef131fa3f59b857217f522fa5ea430d1b707c; 5b0e95bf607ddd59b39f52d3d55e6581c817b530 up to, but not including, a2d8d5647ed854e38f941741aea45b9eb15a6350; and 1 more ranges8ded74c654a982dc8581a17b0caa7fcedb20de69, c9c38066b6446e83668c041702bb639b0ca49363, 094734c7aaa2b36751dc32480a680a4952685e78, 33878ba25e2638bc0c61623d7a05c9ca2b74c039, 404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2, 5e1b2ca6b34939e70fb0785e8222b53cf060016f
LinuxLinux Kernel3.2 up to, but not including, 5.10.265; 5.11 up to, but not including, 5.15.216; 5.16 up to, but not including, 6.1.183; 6.2 up to, but not including, 6.6.148; 6.7 up to, but not including, 6.12.101; 6.13 up to, but not including, 6.18.42; 6.19 up to, but not including, 7.1.6; 7.25.10.265, 5.15.216, 6.1.183, 6.6.148, 6.12.101, 6.18.42

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: btrfs: reject free space cache with more entries than pages When loading a v1 free space cache, __load_free_space_cache() takes num_entries and num_bitmaps straight from the on-disk btrfs_free_space_header. That header is stored in the tree_root under a key with type 0, which the tree-checker has no case for, so neither count is validated before the load trusts it. The load loops num_entries times and maps the next page whenever the current one runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which does io_ctl->pages[io_ctl->index++]. But pages[] is allocated in io_ctl_init() from the cache inode's i_size, not from num_entries: num_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); io_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS); So if num_entries claims more records than the pages can hold, io_ctl->index runs off the end of pages[]. The write side never hits this because io_ctl_add_entry() and io_ctl_add_bitmap() both stop once io_ctl->index >= io_ctl->num_pages; the read side just never had the same check. To trigger it, take a clean cache (num_entries = <N> here), set num_entries in the header to 0x10000, and fix up the leaf checksum so it still passes the tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and pages[] is a 16-pointer (kmalloc-128) array. The load now tries to read 65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the array: BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58 io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820) load_free_space_cache (fs/btrfs/free-space-cache.c:1017) caching_thread (fs/btrfs/block-group.c:880) btrfs_work_helper (fs/btrfs/async-thread.c:312) process_one_work worker_thread kthread ret_from_fork free-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc() at line 565, which is why that is the frame KASAN names. The out-of-bounds slot is then treated as a struct page and handed to crc32c(), so the bad read turns into a GP fault. Add the missing check to io_ctl_check_crc(), which is where both the entry loop and the bitmap loop end up. When num_entries is too large the load now fails like any corrupt cache: __load_free_space_cache() drops it and rebuilds the free space from the extent tree, so a valid cache is never rejected.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Read

The product reads data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that provides appropriate memory abstractions.

More Out-of-bounds Read vulnerabilities (CWE-125)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Read vulnerabilities

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